Little hot water flow in tub/shower? Tricks?


Old 03-14-14, 06:05 AM
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Little hot water flow in tub/shower? Tricks?

I have a 1960s house that I'm selling and have a hot water issue in the main tub. When I turn on the single handle faucet on tons of cold water comes out, but when I turn it left very little hot water comes out. It does not have a hot water limiter. I just replaced the cartridge and when it was out I turned the main back on for a minute to flush the pipes. No luck. I even ran a wire into the hot side pipe when the cartridge was out. Still no luck. The sinks faucets and other faucets in the whole house put out hot water just fine. The house has old galv pipes but maybe 10-15 years ago a plumber put in copper to the galv for a foot or so to install the new faucet.

I can't access the pipes or faucet since it's all enclosed. Is there anyway to "back flush" this line or a trick to clear it? What's going on with this? Thank you!!
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Old 03-14-14, 07:51 AM
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So far you have tried the easy tricks I can think of.

Do you know if the plumber put in shutoff valves for the tub faucet? Unlikely since it's buried in the wall but a possibility. When you mention galvanized pipes it opens the possibility that the inside of the pipes are corroding down to a small size and restricting the flow, for which there is not an easy fix. At that point I'm running new PEX piping.
Old 03-15-14, 12:42 AM
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To be clear, is the hot water flow also slow coming out of the shower head? If so, here's what I did to resolve this at my mother-in-law's older home...

At the hardware store find a 1/2 NPT Iron or Galvanized pipe cap. Remove shower head and screw the cap onto the shower neck, using teflon thread tape. (alternatively, you can remove shower head, put a penny, dime, nickel... largest that will fit....inside the the threaded end of the shower head, then reinstall the shower head). The idea is to block the flow of water coming out the shower neck.

Next, turn the shower's hot/cold handle on, and to the position that would normally give equal hot/cold mix. Then, go to the bathroom sink faucet and remove the screen or water restrictor from the faucet. Finally, turn the sink faucet on, full cold.

Since the shower valve is in the mix position, and flow to the shower head is blocked, when you turn the sink faucet to full-cold, hot water going through the shower valve will get pushed into the cold side of the valve and will eventually backflow out the sink faucet. Let it run for a few minutes and you should start getting some rusty junk in the sink. Turn the sink on/off/on/off quickly. Then, leave it full cold and do the same at the shower valve....on/off/on/off. Then, turn the shower valve full-cold, full-hot, full-cold, full-hot. This on/of action will help loosen up any rust that's stuck in the shower valve. Run sink full-cold again, while shower is in the half and half position for a few more minutes minutes. Repeat until water runs clear from sink faucet. Then, put the shower head back to normal.
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